1. Field of the Invention
The present invention relates generally to digital to analog converters (DACs), and more particularly to a current steering source for a DAC using a master bias network to reduce glitch energy error.
2. Description of the Related Art
A digital to analog converter (DAC) is an electronic circuit that converts an input digital signal to an output analog signal. A numerical value represented by the digital signal input to the DAC corresponds with a magnitude of the analog signal output by the DAC. Various factors determine the performance of a DAC, including speed, resolution, and noise. Speed refers to the amount of time the DAC converts the digital value to a stable analog signal. Resolution refers to the smallest incremental signal that is generated by the DAC and corresponds with the Least Significant Bit (LSB) of the input digital signal. Noise refers to deviations of the output analog signal relative to an expected or desired level, particularly during switching from one digital value to another.
High performance DACs are useful for converting data with high resolution at high frequency and low noise. The current-steering architecture is the architecture of choice for fast-sampling applications, in which each bit or converted data bit is used to switch current from a current source between a pair of nodes. High frequency current steering DACs often exhibit non-ideal behaviors in the form of glitch energy and/or rise time and fall time mismatch particularly during dynamic switching between digital codes. The dynamic performance degradation of a current steering DAC may be caused, for example, by the coupling of control signals through switches to the output. Various methods have been used in an attempt to improve behavior and performance, but many such conventional techniques introduce undesired timing differences or cause charge feed through and injection from switch control signal (e.g., clock signals) thereby causing glitch energy and other distortions at the output.